Dehydration is readily ac c om p lished at room temperat ures. Use of a cold trap (Figure 29)
may substantially reduc e the time required to compl ete the dehydration. The high er the room
temperature, the fast er de hydration takes place. At low room temperatures , a very deep
vacuum is required for boi ling off any moisture. If low ambient temperature s are inv o lved,
contact a qualified ser v ic e representative for th e deh ydration technique s re qui red.
Perform dehydration as follows:
1. Connect a high capa city vacuum pump (5 cfm [ .002 m 3/s] or larger is recommended) to the
refrigerant chargin g valve (Figure 7 and Figure 8). Tubing from th e pump to the machine
should be as short and as lar ge a diameter as possible to pr ov i de least resistance to ga s
flow.
2. Use an absolute press ur e m an ometer or a wet bulb vacuum ind icator to measure the
vacuum. Open the shutoff valve to the vacuum indica tor only when tak ing a reading. Le ave
the valve open for 3 minut es t o allow the indicator vac uum t o equalize with the mach ine
vacuum.
3. Open all isolation valv e s (if present), if the enti re machine is to be dehydra ted.
4. With the machine ambien t temperature at 60 F (15. 6 C) or higher, operate the v ac uu m
pump until the manome te r reads 29.8 in. Hg vac, ref 30 in . ba r. (0.1 psig) (–100.61 kPa) or
a vacuum indicator rea ds 35 F (1.7 C). Operate the pum p an additional 2 hours.
Do not apply greater vacuum than 29.82 in. Hg vac (757.4 mm Hg) or go below 33 F (.56 C)